Up to now, in coping with rapidly increasing utilization of an electronic medium, such as picture, image or multimedia, an electronic watermark is embedded electronically into a picture or image for facilitating discrimination of a data source.
The furnisher of the electronic medium embeds electronic watermark signals for identifying the furnisher in the data of the electronic medium it supplies. As the electronic watermark signals are detected by the software or the hardware, the furnisher proves that is an owner of the copyright for supervising and managing the copyright.
The above-described method for inserting and extracting the aforementioned electronic watermark is disclosed in, for example, the JP Patent Kokai JP-A-10-145757 or JP Patent Kokai JP-A-10-191330.